Grant amount：\16490000 （ Direct Cost: \15800000 、 Indirect Cost：\690000 ）

Flagellated bacteria like Sal. Typhimurium swims by rotating helical flagella filaments with bundling and synchronizing them each other. Because axs of bacterial motors directed in different way, flexible joint part is required between motor and flagella filament. It is known that bacterial hook work as a universal joint of this part. However its mechanical feature like rigidity is not known exactly. Here we measured modulus of rigidity by using polyhook filament, length about 1μm, from mutant Sal. Typhimurium(SWJ108). Purified polyhook filaments were frozen rapidly in liquid ethane and freeze dried. Distribution of helix pitch and diameter were evaluated from electron micrographs of shadowed images. We got value of 95±23nm for helix pitch and 31±9.9nm for diameter of polyhook filament. We also measured fluctuation of helical pitch and diameter of flagella filament from negative stained samples. By comparing fluctuation of polyhook and flagella filaments, we have calculated the ratio of rigidity as G_<flagella>/G<hook>=120. According to the literature value of flagella filament rigidity, 3.8×10^9Pa, we obtained rigidity of polyhook as 3.3×10^7Pa. We also tried to measure the rigidity of flagella in solution directly using thin glass capillary. Fluorescent labeled flagella filament was fixed by anti-flagellin adsorbed on a glass capillary of diameter less than 1μm. Tension in pN range was measured from bending deformation of glass capillary under fluorescent microscope. We are now accumulating the results in this process. We are going to measure rigidity of super-poly hook which has length of few micro-meter by the same method.

researchmap

Grant amount：\3600000 （ Direct Cost: \3600000 ）

In this research, we investigated the driving, lubrication and self assembled mechanism of bacterial flagellar motor in order to develop new principle of nanomachine architecture. In nanoscale world, different kind of physical effects have essential roles on driving, lubrication and self assembled mechanism of machines. We did not know the guiding principle to construct nonomachine at the starting point of the study. Bacterial having flagellar motor sometimes called living nanomachine as it has motor, journal bearing universal joint and screw. Our main idea is to get the precise knowledge of the mechanism of bacterial flagellar motor and utilizing these mechanisms to the driving, lubrication and self assembled system of nanomachines.
In a previous study, we estimated lubrication mechanism of bacterial flagellar. By using theory of the classical hydrodynamic lubrication, we calculated load capacitance. Resulting load capacitance is order of 0.1pN( x 10^<-12>N) and this values is not adequate to compensate driving force (0.5pN) Furthermore, intermolecular force between rod and journal becomes order of 10^2pN that is far bigger than load generated by driving force.
Thus, we concluded that new lubrication mechanism must be introduced to explain the behavior of PL ring. We proposed use of diffusive double layer as possible candidate of lubrication mechanism. We estimated the load capacitance generated by this effect and showed the adequate amount of repulsive force can be obtained by this mechanism.
We formulated new lubrication mechanism using the effects of diffusive double layer that is known as the origin of stability in hydrophobic colloidal solution. It is shown that this mechanism not only gives enough load capacitance to compensate the various forces between journal of rod in axial and radial direction but also gives driving force of self assembled system.

researchmap

Grant amount：\3200000 （ Direct Cost: \3200000 ）

本研究の目的は、吸着分子膜のレオロジー特性を考慮した境界潤滑領域の摩擦特性を定量的に予測するために必要な境界膜の被覆率を測定することである。
境界潤滑膜の摩擦特性をあきらかにするために、ある条件(すべり速度,温度)の下で,吸着膜がどの程度の割合で接触面に存在するか(接触面での被覆率)を明らかにする必要がある。本研究では、軽荷重(mN、MPaオーダ)・極低速(μm/s)における被覆状態を、エリプソメトリおよび,ブリュースター角顕微鏡によって,摩擦直後のしゅう動面を観察することによって測定する。また、従来行ってきた100%被覆している状態(LB膜類似吸着膜)の摩擦特性から吸着膜のレオロジー特性を推定することで,混合潤滑の総合的な摩擦特性を説明できるようになるが,装置の改良による被覆率測定法の確立と,いくつかのパラメータを振った場合の境界膜の被覆率測定を試みた.
エリプソメトリ・ブリュースター角顕微鏡測定で問題となった粗さのある面の微小な面の傾きによる影響は除去するのが非常に難しいことがわかった.
また境界膜(吸着膜)の特性,とくに吸着膜の空間的な分布と表面の高さ分布を把握するために既存の走査型プローブ顕微鏡のAFM, FFM,交流FFMなどを使って,面圧,しゅう動速度,温度をパラメータとしてしゅう動時の被覆率がどのように変化するのかについてデータを収集し被覆率を推定するための摩擦係数のマッピングを行った.

researchmap

Grant amount：\3500000 （ Direct Cost: \3500000 ）

In this research, we investigated the driving and lubrication mechanism of bacterial flagellar motor in order to develop new guiding principle of nanomachine construction.
In nanoscale, different kind of physical effects has essential role on driving and lubrication mechanism of machines. Until now we do not know the guiding principle to construct nonomachine. Bacterial having flagellar motor sometimes called living nanomachine as it has motor, journal bearing universal joint and screw. Our main idea is to know the mechanism of bacterial flagellar motor and utilizing these mechanisms to the driving and lubrication system of nanomachines.
In a recent study, we estimated parameters in the tribology of the PL ring. By using theory of the classical hydrodynamic lubrication, we calculated load capacitance. Resulting load capacitance is order of 0.1pN(×10^<-12>N) and this values is not adequate to compensate driving force (0.5pN) Furthermore, intermolecular force between rod and journal becomes order of 10^2pN that is far bigger than load generated by driving force.
Thus, we concluded that new lubrication mechanism must be introduced to explain the behavior of PL ring. We proposed use of diffusive double layer as possible candidate of lubrication mechanism. We estimated the load capacitance generated by this effect and showed the adequate amount of repulsive force can be obtained by this mechanism We formulated new lubrication mechanism using the effects of diffusive double layer that is known as the origin of stability in hydrophobic colloidal solution. It is shown that this mechanism gives enough load capacitance to compensate the various forces between journal and rod.

researchmap

Grant amount：\3600000 （ Direct Cost: \3600000 ）

The Objective of this project is the experimental verification of Burwell-Strang's hypothesis, that is "abrupt increase of ware rate is caused by transition of yield area from asperity summit level to apparent contact area level".
To achieve the objective, we tried these approaches :
1.We developed a test apparatus for observation of deformation near an asperity using commercial metal microscope. In this test, we measured deformation of mesh previously made on side of softer surface after indentation and dragging between wedge of hard body and flat soft surface.
2.We got good agreement between numerical results of our model used by slip line field theory and those of finite element method. We refined our model using results of FEM. We also calculated distribution of real contact spots under normal and shear stress.
3.We also developed a contact microscope using total reflection method, in order to predict the transition pressure of contact between rough surface and smooth surface. In this apparatus, we can slide contact area in addition to normal load. For preliminary study, we observed growth and increase of real contact spots on blast finished random rough surface under normal load. The results indicated that apparatus could estimate transition pressure and verify our theory.
We are going to study the effect of normal and shear stress on change of real contact spot. We will also try to develop our theory that can predict wear transition pressure under extensive condition.

researchmap

Grant amount：\2800000 （ Direct Cost: \2800000 ）

本研究では、宇宙環境下の摺動部へ、最小限必要な液体潤滑を給油する方法の一つとして、液体潤滑剤と給油系材料表面との間の表面エネルギーの勾配、例えば濡れ性の局所的な違い、を利用した液体輸送法について提案し、その成立条件、給油量、実用化する場合の問題点を把握し、本給油法の実現可能性を評価することを目的として、本年は大気圧下において表面エネルギー勾配をもった表面を試作し、宇宙環境下で使用されている潤滑剤をその表面に滴下したときに油膜が広がる様子の測定を行うことを目標とした。
第一の目標である「表面エネルギー勾配をもった表面の試作」では、平成14年度の研究結果より「表面コーティング」が最も現実的という結論に達したので、今年度はそのコーティグ膜の試作を行った。コーティング膜としては、DLC(Diamond Like Carbon)が強度も十分にあり、製膜時に原料ガスのメタン以外にフッ化炭素ガスを添加して、その濃度によって膜中のフッ素量を制御できるので、それを選択した。ここでは、さらに表面エネルギーを制御するために、アルゴンと酸素のプラズマに暴露した。その結果、濡れ性の異なる表面を作成することができた。そこで、試験用の表面として、表面エネルギーの異なる薄膜を帯状に配置した表面を準備した。
第二の目標である「給油状態評価」では、液滴界面の広がり状態の把握に光学顕微鏡による「気液界面観察」を,給油状態の確認にレーザー誘起蛍光法および白色光源と分光計を用いた光干渉法による「油膜厚さ計測」を試みた。その結果、液滴が試料表面を広がる様子が観察されたとともに、高分解能で表面に付着した油膜厚さを数μmから10nmの広い範囲にわたって計測することができ、表面エネルギーの異なる薄膜を帯状に配置した表面でも、液体輸送に有効であることが確認できた。

researchmap

Grant amount：\900000 （ Direct Cost: \900000 ）

The threshold of load condition from light to heavy that Burwell and Strang proposed in 1952 as a concept of the mode transition from mild to severe wear, are tried to be estimated considering isotropic and Gaussian surface, and verification by direct observation. In brief, the threshold condition is expressed as the critical pressure at which the nominal contact area is wholly covered with the yielding area. This critical pressure has been calculated using stochastic rough surface contact theory and Johnson's Elastic Plastic Indentation model with Chang-Etsion's analysis. Individual summit of rough asperity has been assumed to be a sphericity and all of them to have the same radius. Analysis has been developed the effect of slip on rough surface contact. The contact is regarded as 2D and is assumed as that between rough surface and plane to apply the slip line field theory.
Micro-sliding mechanism are designed for the system which is able to give the normal load and shearing load to observe the realistic contact points. At the beginning the piezo-scanning stage would be planned for nano-scaled actuator, but it is difficult to decrease the shear deformation at their contact, observe the status of adhesion due to wear of the end of the 400 mm traveling by motor actuated slider.
In the experiments, normal force and tangential force are measured simultaneously. The effects of mechanical characteristics (normal pressure, shear stress, the Young's modulus, hardness and shear strength of surfaces) , geometric characteristics (surface roughness and shape) are investigated in the discussion of the wear mode. The direct observation of the realistic contact area, which mean the shape, number and area of contacted asperity is planed in the near future.

researchmap

Grant amount：\3500000 （ Direct Cost: \3500000 ）

From the viewpoint of mechanical engineering, the bacterial flagellar motor has several interesting features ; it rotates at a maximum speed of 17,000 HZ, and the diameter of the rotor is about 50 nm. In nature, the driving system using rotational motion is found only in single-celled organisms bacteria, while beating motion dominates the non-bacterial world.
Since life chooses the more efficient mechanism in the process of evolution, it is interesting to know the reasons why bacteria chose rotational motion rather than beating motion.
On the other hand, motors are widely used as driving systems in engineering. When we consider the difficulty of lubrication in microtribology which occurs in a world as small as bacteria, knowledge about the f1agellar motor will be useful to solve the problems.
In the 20th century, tribology and lubrication engineering on the macroscale have reached a paradigm that most of the solid frictions in engineering can be well described by Coulomb-Amonton's law and that the best strategy of lubrication is fluid film lubrication. Here, deviations from Coulomb's law such as the friction of rubber or super-lubricity are considered to be exceptional cases.
Now, entering the 21st century, the circumstances around tribology are drastically changing. Since the paradigm is not always applicable to newly emerging areas such as microtribology, we have to employ some other paradigms for friction and lubrication.
In microtribology, friction between ideal crystalline surfaces may sometimes occur. Molecular forces would play an essential role in this kind of friction. Therefore, Coulomb's law is not powerful anymore ; as it is an experimental rule for solid friction. Molecular forces affect the behavior of liquids in molecularly thin liquid films. When thin film viscosity (or a viscosity rise) is duced by molecular forces, the fluid film lubrication method will not be the best anymore. Until now, we have not obtained enough knowledge about the lubrication in micromachines.
In the flagellar motor of some bacterial species, there is a bushing, called the PL ring, which allows the rotating shaft to penetrate the rigid cell wall. The existence of the PL ring suggests that our classical method of lubrication might be still valid in microtribology. In a recent study, we calculated parameters in the tribology of the PL ring using theory of the classical hydrodynamic lubrication and the parameter values in thin film viscosity. The results showed that the friction values thus calculated are too high to operate the motor at high speeds, indicating invalidity of the classical method.
In this study, we show that the ordinary theory for hydrodynamic lubrication is not an adequate tool for analysis of lubrication in the PL ring. We also calculate the scale invariance of the Stokes equation and consider other possible lubrication mechanisms.

researchmap

Grant amount：\3800000 （ Direct Cost: \3800000 ）

It is in progress to switch to chlorine free refrigerants, since CFCs(Chloro Fluoro Carbons) containing chlorine are considered as causes of ozone depletion and global warming. However, there are several difficulties to alternate refrigerants Particularly, poor solubility of refrigerant in usual mineral oil and poor lubricity of Freon gas are serious. Therefore, it is necessary to improve the lubrication design of sliding parts and to develop the sliding materials and refrigeration oils for alternative refrigerants. A rolling piston type of rotary compressor is widely used as a small refrigerator and air-conditioner for household use because of high volumetric efficiency and compactness. Although the alternation of refrigerants is in progress now, it is indispensable to soluve the lubrication problems of vane tip which has the most severe lubrication condition in refrigerant compressors.
In this project for purpose of developing lubrication design tool for rotary refrigerant compressors, rheological behavior of boundary lubricant film with refrigent molecules.
In addition to that, the coefficients of boundary friction under mixed lubrication in refrigerant atmosphere are estimated by comparing the measured frictional characteristics with the calculated ones and the oil film under elastohydrodynamic lubrication in refrigerant atmosphere are observed by FT-IR microscope in order to obtain unknown parameters of the analysis. Then the validity of this analytical method is shown by comparing metal contact ratios measured for an actual compressor with those of the calculated results. After that, the computer simulations are performed for the lubrication condition in order to suggest guidelines for the lubrication design of the rotary refrigerant compressors.

researchmap

Grant amount：\6900000 （ Direct Cost: \6900000 ）

Sliding contact at edge with large defomation in many mechanical elements (journal bearings, piston pumps , etc). Analysis method considering gross deformation for this problem is developed in this project. Precise contact FEM analysis without surface roughness, microscopic contact analysis at surface roughness oil film pressure and their comnination are Discussed.
The analysis model under the conditions of piston-cylinder contact in piston pump/motor is used. First, we handle FEM contact with smaller mesh near contact point, to discuss the appropriate mesh size for contact pressure or deformation., then calculate oil film pressure considering deformation.. The fomulation of oil film thickness are for simple shape contact (circle or cylindrical) simple oil film analysis (ie. Ertl-Grubin theory) are for non-simple shape like the edge of piston. It is adapted method for EHL film at the element, which has complex shape or large displacement. Experimental examinations, measurement of displacement by capacity meter and contact area by IR thermalscope are testing now, so there is no applicable results.

researchmap

Grant amount：\12600000 （ Direct Cost: \12600000 ）

The tribotester developed in this grant consists of a pressure chamber, a tribotesting part and detection of friction and load. The pressure chamber can withstand up to 5 MPa in refrigerant gas pressure and can control the temperature of the oil bath in the tester from 10 to 80゜C and maintain a constant value within (]SY.+-。[)1゜C.The tribotesting part is a standard ring-on-block type Farex friction testor. The sliding speed ranges from 75x10<@D1-3@>D1 up to 7.3m/s, which covers the whole mixed lubrication region for new refregerants and lubricants under practical temperature, are available with a DC servo motor with 0.85 KW power output. The friction force and the contact load can be detected from the outside through bellows seals.
The boundary friction coefficients for various new refrigerant and new lubricants have been obtained in the mixed lubrication region where the tribo-elements in practical compressor state in the most possibility, by means of the mixed lubrication analysis under hard EHL regime.
The calculated results and the measured results by means of the contact electric resistance have been compared and agreed qualitatively. It is found that the combination of the tribotester and the mixed lubrication analysis is quite useful for selecting new lubricants and new materials against new refrigerants.

researchmap

Grant amount：\2500000 （ Direct Cost: \2500000 ）

混合潤滑を解析する上で、流体潤滑寄与分と境界潤滑寄与分の両者は同等の精度で取り扱わなければならないが、従来の解析においては、流体潤滑部分と比較して境界潤滑部分の評価が不十分である.特に表面粗さの形状による接触状態およびそれに伴う摩擦力のモデル化が十分でない.このため,製作した高精度スピンドル装置を用いたボール・オン・ディスク型摩擦試験機を用い,磁気記録装置用ディスクの平滑面に対し,いくつかの粗さ形状のもった軸受鋼球を接触させることによってによって摩擦特性測定し,粗さ形状によって実験結果を整理した.
まず,粗さ形状を,統計分布のみで表し,整理した.なお,吸着膜の特性については,被覆率をLangmuir吸着式から,せん断強さをEyring粘性モデルから導かれるBriscoeのLangmuir膜のモデルを用いる申請者らのモデルを用いた.
実験においては,ボール・オン・ディスク摩擦試験機による実験結果が上記モデルと定性的に一致し,定量的にも近い値が得られた.また,さらに既存の実験装置の改造によりボールオンディスク型の実験装置を製作したが,本年度は実験装置の動作確認と,特性評価に終わった。解析に関しては,実験結果と比較して満足される結果は得られず,ボールオンディスク摩擦試験機による実験とともに今後の課題である.

researchmap

Grant amount：\2200000 （ Direct Cost: \2200000 ）

混合潤滑を解析する上で、流体潤滑寄与分と境界潤滑寄与分の両者は同等の精度で取り扱わなければならないが、従来の解析においては、流体潤滑部分と比較して境界潤滑部分の評価が不十分であるため,本研究では境界潤滑膜のせん断特性のうち、境界膜の被覆率と膜自身のせん強さに着目し、境界潤滑を含む一般的な混合潤滑モデルの構築、および数値シミュレーションを行ない、混合潤滑下での境界潤滑膜の吸着特性、とくに吸着膜の被覆率とせん強さを定量的に評価し,二円筒式摩擦試験機および今回改造によって製作されたボールオンディスク式摩擦試験機によって測定される摩擦特性と比較,検討した.
まず,油性添加剤の吸着膜について,被覆率をLangmuir吸着式から,せん断強さをEyring粘性モデルから導かれるBriscoeのLangmuir膜のモデルを用いて定量化した。また,その吸着膜モデルを,申請者らの提案している混合潤滑解析モデルに組込み,計算した結果,油膜温度,すべり速度,および荷重の影響を定性的に説明することが出来た。
実験においては,二円筒試験機による実験結果が上記モデルと定性的に一致し,定量的にも近い値が得られた。また,さらに既存の実験装置の改造によりボールオンディスク型の実験装置を製作したが,本年度は実験装置の動作確認と,特性評価に終わった。分子力学を用いた吸着膜の被覆率およびせん断強さの計算は,解析モデルおよび実験結果と比較して満足される結果は得られず,ボールオンディスク摩擦試験機による実験とともに今後の課題である。

researchmap

Grant type：Competitive

researchmap

Grant type：Competitive

researchmap

Grant type：Competitive

researchmap

Grant type：Competitive

researchmap

Grant type：Competitive

researchmap

Grant type：Competitive

researchmap